Electrochemical Method for Producing and Storing Hydrogen by the Redox of Zinc and Water

ABSTRACT

Disclosed herein is an electrochemical method for producing and storing hydrogen, which is a closed system consisting of a gas-generating electrode, an electrolyte and a zinc electrode, the gas-generating electrode and zinc electrode are connected respectively to the external circuits; characterized in that switching on the external circuit of the gas-generating electrode and zinc electrode the hydrogen is to be released, the reduction reaction of water occurs on the gas-generating electrode producing hydrogen; zinc is oxidized on the zinc electrode generating the oxidation products of zinc; when the hydrogen is to be stored, supplementary water is supplied to the closed system, the negative pole of power source is connected to the external circuit of the zinc electrode, and the positive pole of power source is connected to the external circuit of the gas-generating electrode, switching on the direct current, the reduction reaction of zinc occurs on the zinc electrode, the oxidation products of zinc are reduced into zinc, renew the zinc electrode, the oxidation reaction of water occurs on the gas-generating electrode, the oxygen is generated and discharged. A simple and convenient process and widely applied are property of the present invention. It suits to provide hydrogen for hydrogen fuel cells. While providing the hydrogen, it can also generate electricity as secondary product, which generates the electricity together with a fuel cell.

FIELD OF THE INVENTION

This invention relates to the technology of producing and storinghydrogen, particularly to the electrochemical method for producing andstoring hydrogen by the redox of zinc and water.

BACKGROUND OF THE INVENTION

As consumption of petrochemical fuel and exhaustion of reserves ofpetrochemical fuel are daily on the increase, environmental protectionhas been gradually emphasized. Primary energy source includingpetroleum, coal and natural gas shall be finally replaced by clean andrenewable energy source such as solar energy, wind energy, energy fromthe sea, biological energy, etc. As secondary energy source, withoutpollution, hydrogen energy is greatly valued by every country in theworld due to considerable advantages of being rich in its resource,having high combustion heat quantity, producing water as its combustionproduct, and having no environmental pollution, etc. Especially, ahydrogen-oxygen (air) fuel cell that uses hydrogen as its fuel, rose inrecent years, is one kind of highly efficient, clean and long-lifeelectricity generation device, which will become the ideal power sourceof portable electronic products and electrically driven vehicles. Maincause of hindering its popularization is lack of appropriate source ofhydrogen. At present, there are four main ways to supply the hydrogenfor the fuel cell and that of: I. High-pressure hydrogen bottle method.2. Low temperature fluidized method. 3. Hydrocarbon fuel reformingmethod; 4. Metal hydrides storing-hydrogen method. Wherein, thehigh-pressure hydrogen bottle method and the low temperature fluidizedmethod have some serious shortcomings such as high cost, being poor inthe aspect of safety etc. The hydrocarbon fuel reforming method, beingpoor in the aspect of purity of hydrogen gas, needs the relatively hightemperature, the large equipment. Due to safety property, the metalhydrides storing-hydrogen method plays an importance role in theresearch and development of storing-hydrogen technology. However, thestoring-hydrogen alloy is very expensive and easy to become chalking inthe course of filling, which is relatively complicated, and releasingthe hydrogen gas. Nowadays, a patent, in name of “Electrochemical Methodand Equipment for Producing and Storing Hydrogen by Redox ofAluminum-Water” (its application number is 02148850.9) provided twophases circulating filtering closed system consisted of an aluminumalloy electrode-electrolyte-highly active hydrogen-generating catalyticplate electrode with advantages being of highly efficient, safe, withoutenvironment pollution, etc. However, its shortcomings are as follows:the aluminum alloy electrode is a disposable consumable material; it isneeded to replace the aluminum alloy electrode after hydrogen generationevery time; it has a high consumption; in addition, produced aluminumoxide must be eliminated by pump circulation filtering, and the hydrogengeneration course is relatively complicated, which increases the cost.

SUMMARY OF THE INVENTION

The objective of the invention is to provide the electrochemical methodfor producing and storing hydrogen by the redox of zinc and water withhigh reliability, low cost, simple and convenient process wherein thezinc electrode can be used repeatedly.

In order to fulfill the objective above, the technology program of theinvention is as follows.

The method comprises the closed system consisted of the gas-generatingelectrode-electrolyte-zinc electrode. Both the gas-generating electrodeand the zinc electrode are connected respectively to the externalcircuit. When the hydrogen is to be produced, the external circuits ofthe gas-generating electrode and zinc electrode are connected, water isreduced into hydrogen on the gas-generating electrode, the reductionreaction of water occurs on the gas-generating electrode, zinc isoxidized on the zinc electrode generating the oxidation products ofzinc. Switching off the external circuit, the releasing process ofhydrogen gas stops immediately; when the hydrogen is to be stored,supplementary water is supplied to the closed system, and then thenegative pole of power source is connected to the external circuit ofzinc electrode, and the positive pole of power source is connected tothe external circuit of gas-generating electrode, then the directcurrent is applied, the oxidation products of zinc are reduced into zincon the zinc electrode, and water is oxidized into oxygen on thegas-generating electrode, and then the oxygen is released.

The gas-generating electrode used in this invention consists of thehydrogen-generating electrode and oxygen-generating electrode, or thehydrogen-generating electrode that is concurrently as theoxygen-generating electrode. The former uses a system that consists ofthe oxygen-generating electrode, electrolyte, zinc electrode,electrolyte and hydrogen-generating electrode or the oxygen-generatingelectrode-electrolyte-zinc electrode-electrolyte-hydrogen-generatingelectrode. When the hydrogen is to be released, the external circuits ofthe hydrogen-generating electrode and zinc electrode is connected; whenthe hydrogen is to be stored, the negative pole of power source isconnected to the external circuit of zinc electrode, the positive poleof power source is connected to the external circuit ofoxygen-generating electrode. The latter uses a system that consists ofthe zinc electrode, electrolyte, hydrogen-generating electrode that isconcurrently as the oxygen-generating electrode or the zincelectrode-electrolyte-hydrogen-generating electrode, whereinhydrogen-generating electrode is concurrently used as theoxygen-generating electrode. When the hydrogen is to be released, thezinc electrode and hydrogen-generating electrode that is concurrentlyused as the oxygen-generating electrode are connected to the externalcircuit, and when the hydrogen is to be stored, the negative pole ofpower source is connected to the external circuit of zinc electrode, thepositive pole of power source is connected to the external circuit ofhydrogen-generating electrode that is concurrently used as theoxygen-generating electrode.

Generally, the electrolyte used in this invention is strong alkalineelectrolyte aqueous solution so that the zinc electrode has goodreversibility and great capability to discharge under the heavy electriccurrent. The strong alkaline electrolyte is taken as an examplethereafter to explain reaction principle of the electrochemistryoccurred in the system for producing and storing hydrogen by the redoxof zinc and water.

1. When the hydrogen is to be released, the reaction occurred is asfollows.

Zinc Electrode:

Zn+2OH⁻−2e→Zn(OH)₂(E ⁰=−1.249 V)

Or, Zn+2O H⁻−2e→ZnO+H₂O(E ⁰=−1.260 V)

Gas-Generating Electrode:

2H₂O+2e2O H⁻+H₂ ↑ (E ⁰=−0.828 V)

The overall reaction is: Zn+2H₂O→Zn(OH)₂+H₂↑ (ΔE ⁰=0.421 V)

Or, Zn+2H₂O→ZnO+H₂ ↑ (ΔE ⁰=0.432 V)

Essentially, it is a course that water is reduced and zinc is oxidizedto generate Zn (OH)₂ or ZnO, producing the hydrogen and electric energy.The electric current with certain voltage can be obtained in theexternal circuit, and the theoretical electric potential is 0.42-0.43 V.The produced quantity of hydrogen can be controlled conveniently bycontrolling the electric current of the external circuit.

2. When the hydrogen is to be stored, the reaction occurred is asfollows.

Zinc Electrode:

Zn(OH)₂+2e→Zn+2OH⁻(E ⁰=−1.249 V)

Or, ZnO+H₂O+2e→Zn+2O H⁻(E ⁰=−1.260 V)

Gas-Generating Electrode:

2O H⁻−2e→2H₂O+1/2O2 ↑ (E ⁰=0.401 V)

The overall reaction is: Zn(OH)₂→Zn+H₂O ↑ +1/2O2 ↑ (ΔE⁰=−1.650 V)

Or, ZnO→Zn+1/2O2 ↑ (ΔE ⁰=−1.661 V)

Essentially, it is a course that Zn (OH)₂ or ZnO is electrolyzed andreduced into Zn to produce the oxygen. Due to a great overpotential, thepractical decomposition voltage will be higher than the theoreticalelectric potential of 1.65-1.66 V, which can be up to about 2 V.

In the conditions of using other kinds of electrolytes, or in theinitial stage of using the strong alkaline electrolyte, when zincdischarges, the zinc oxidation products that differ from Zn (OH)₂ or ZnOcan be generated. But the course and principle of charging anddischarging of producing and storing the hydrogen are the same as theexample mentioned above.

The zinc electrodes used in the method for producing and storinghydrogen in this invention are made of the zinc active substance,adhesive, additives and current-collecting device by using many physicaland chemical methods such as the compacting, applying paste,agglomerating, boxing (piping), foaming, electrodeposition technologyetc. The zinc active substance can be composed of the zinc compoundssuch as the zinc alloy powder, zinc oxide, zinc hydroxide, zincate, etc.or their combinations; the adhesive selected from the group consistingof carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE)emulsion, polyvinyl alcohol (PVA), hydroxypropyl emthylcellulose (HPMC),polyethylene oxide (PEO), polyacrylic acid (PAA), polyvinylidenefluoride (PVDF), hexafluoropropylene, or mixtures thereof; the additivesselected from the group consisting of zinc oxide, calcium oxide,magnesium oxide, cadmium oxide, alumina, bismuth compounds, leadcompounds, calcium hydroxide, graphite powder, acetylene black, carbonpowder, electric carbon black, active carbon powder, short-cut fiber,carbon fibers, or mixtures thereof; the current-collecting device can bemade of the foamed metal, metal mesh, metal tape (metal can be puremetal or alloy) by using the physical and chemical methods such aselectroplating, composite plating to treat the surface oft metal; Forexample, they may be the foamed brass, lead plating or tin platingpunched brass strip, brass screen. The zinc electrode described abovecan be the flaky and porous powder structure and preferably porouspowder structure.

The electrolyte used in the method for producing and storing hydrogen inthis invention is treated by using an aqueous solution electrolyte withthe battery diaphragm to absorb. The pH of the aqueous solution is morethan 4; The concentration of the aqueous solution is in range of 0.05Mol/L˜15 Mol/L. The aqueous solution can be selected from the hydroxideaqueous solution of alkali metal or alkaline earth metal or theirmixtures, and preferably KOH, NaOH aqueous solution or their mixtures,or the carbonate, sulfate, fluoride salt aqueous solution of alkalimetal or alkaline earth metal or their mixtures, or the mixture of theirhydroxide aqueous solution; the diaphragm can be made of any oneselected from the group consisting of cellulose hydrate film,polyethylene graft film, cellophane paper, nylon cloth, hydratedcellulose paper, cotton paper, potassium titanate paper, polyethylenefelt, zirconia fiber paper, vinyl on non-woven fabric, or mixturesthereof to form composite membrane.

The lower overpotential active hydrogen-generating electrode forhydrogen-generating can be used as the hydrogen-generating electrode inthis invention. The active hydrogen-generating electrode is made of puremetal, metal oxide, alloy or metal and the composite material formed byalloy and oxide, by using physical and chemical methods such as theelectroplating, composite plating, thermal decomposition, ion plating,ion implantation, ion sputtering, chemical plating, foamed metaltechnology, and also by comprehensively using the two or three kinds oftechnologies described above. Its composition can be the pure metalsselected from the group consisting of lower overpotential metal forhydrogen-generating such as Ni, Co, Fe, Mo, W, Pt, Pd, Ru oxides such asRuO₂, TiO₂, ZrO2, alloys such as Ni—Mo, Ni—B, Ni—P, Ni—NiS, Ni—Pt,Ni—Ru, Co—Mo, Ni-Wo, Xi-Sn, Mo—W, Co—W, Ni-storing-hydrogen alloy, aswell as Ni—P—Co—Mo—W, Ni—Co—Mo, Ni—Co—Mo—W, Ni—P—Mo—Co, Ni—P—W,Ni—P—Co—Mo—W, Ni.B—Co, Ni—B—Mo, Hi-B—Co—Mo, Ni—B—Co—Mo—W, Ni—B—W, Ni—Co—storing-hydrogen alloy, the composite materials formed by the metal oralloy with the oxide, in terms of the composite materials that adheresto the RuO₂, ZrO₂, carbon fine particles with the pure metal or alloymentioned above or pure metal and alloy mixtures, such as Ni—RuO₂,Ni—Mo—RuO₂, Ni—NiS, Ni—Mo—W—RuO₂. The oxygen-generating electrode ismade of metal steel, iron, nickel with the structures of mesh, strip,plate, sheet, foamed metal, by using the nickel plating or sulfur coatednickel plating method, or is the titanium-base platinum group oxideelectrode, iridium system coating titanium electrode, manganese dioxidecoating titanium electrode, perovskite structure of oxide electrode,which have a special catalytic force to the oxygen-generating course.

The hydrogen-generating electrode that is concurrently as theoxygen-generating electrode used in this invention can be made of themetallic materials such as the steel, iron, nickel with the structuressuch as mesh, strip, plate, sheet, foamed metal, and treated by usingthe physical and chemical methods such as the nickel plating or sulfurcoated nickel plating.

The hydrogen-generating electrode, oxygen-generating electrode andhydrogen-generating that is concurrently as the oxygen-generatingelectrode described above, can be made into the a variety of structuressuch as flaky, meshy, porous structures, and the gas diffusion electrodestructure that is similar to the fuel cell electrode can be selected.

The following two kinds of devices can be made according to thisinvention:

1. A device consists of a storage tank, liquid control valve, fillingopening, hydrogen collecting chamber, hydrogen outlet, oxygen outlet,zinc electrode, compartment separator plate, hydrogen-generatingelectrode, oxygen-generating electrode and dash pot. The storage tank islocated above the hydrogen collecting chamber. The electrolytic cellsystem, provided with a plurality of electrode chambers, is installed atthe lower part of the hydrogen collecting chamber. The number of thechambers is determined according to the amount required to produce thehydrogen gas and the release rate of the hydrogen gas. Thehydrogen-generating electrode, zinc electrode and oxygen-generatingelectrode are uniformly arranged in each electrode chamber. Eachelectrode chamber, which separates the electrodes from each other, isfilled with diaphragms. Each electrode is connected to the externalcircuit. There is the filling opening on the storage tank for theelectrolyte aqueous solution or water supplementing. The hydrogen outletis set on the hydrogen collecting chamber, and the dash pot is equippedon the lower part of the electrolytic cell system, which is used forkeeping the same liquor level of the electrolyte in the electrolyticcell system. When the hydrogen gas is to be released, the liquid controlvalve is firstly opened so as to make the electrolyte of the storagetank flowing into every electrode chamber and the dash pot in theelectrolytic cell system through a duct on the bottom of storage tank,then to switch on the external circuit of the zinc electrode andhydrogen-generating electrode and form a loop. A large quantity ofhydrogen gas begins to be produced on the hydrogen-generating electrode.The hydrogen gas is collected in the hydrogen collecting chamber andflows out through the hydrogen outlet. While the hydrogen gas flows out,the electric energy is sent out from the positive pole and negative poleof the electrochemical system for producing and storing hydrogen. Byswitching off the external circuit of the zinc electrode andhydrogen-generating electrode, the system immediately stops producinghydrogen. When the hydrogen gas is to be stored, at first supplementarysufficient water is applied into the electrolytic cell system throughthe filling opening, and then connect the positive pole of power sourceto the external circuit of the oxygen-generating electrode, connect thenegative pole to the external circuit of the zinc electrode, switch onthe direct current, the zinc electrode begins to be reduced into zincand the oxygen-generating electrode begins to largely produce oxygen.The oxygen discharges directly from the oxygen outlet.

2. The device can be a structure that consists of the storage tank, theliquid control valve, the filling opening, the hydrogen collectingchamber, hydrogen outlet, the oxygen outlet, zinc electrode, thecompartment separator plate, the hydrogen-generating electrode that isconcurrently as the oxygen-generating electrode and the dash pot. Thestorage tank is located above the hydrogen collecting chamber. Theelectrolytic cell system, provided with a plurality of electrodechambers, is installed at the lower part of the hydrogen collectingchamber. The number of the chambers is determined according to theamount required to produce the hydrogen gas and the release rate of thehydrogen gas. The zinc electrode and hydrogen-generating electrode thatis concurrently as the oxygen-generating electrode are uniformlyarranged in each electrode chamber. Those electrodes are separated fromeach other. Each electrode is connected to the external circuit. Eachelectrode chamber is filled with diaphragms, which separates theelectrodes from each other. There is the filling opening on the storagetank for the electrolyte aqueous solution or water supplementing. Thehydrogen outlet is set on the hydrogen collecting chamber, and the dashpot is equipped on the lower part of the electrolytic cell system, whichis used for keeping the same liquor level of the electrolyte in theelectrolytic cell system. When the hydrogen gas is to be produced, theliquid control valve is firstly opened to make the electrolyte in thestorage tank flowing into every electrode chamber and the dash pot inthe electrolytic cell system through the duct on the bottom of storagetank, then to switch on the external circuit of the zinc electrode andhydrogen-generating that is concurrently as the oxygen-generatingelectrode and form a loop. A large quantity of hydrogen gas begins to beproduced on the hydrogen generating electrode that is concurrently asthe oxygen-generating electrode. The hydrogen gas is collected in thehydrogen collecting chamber and flows out through the hydrogen outlet.While the hydrogen gas flows out, the electric energy is sent out fromthe positive pole and negative pole of the electrochemical system forproducing and storing hydrogen. By switching off the external circuit ofthe zinc electrode and hydrogen-generating electrode, the systemimmediately stops producing hydrogen. When the hydrogen gas is to bestored, at first supplementary sufficient water is applied into theelectrolytic cell system through the filling opening, and then toconnect the positive pole of power source to the external circuit of theoxygen-generating electrode, connect the negative pole to the externalcircuit of the zinc electrode, and switch on the direct current, thezinc electrode begins to be reduced into zinc and thehydrogen-generating that is concurrently as the oxygen-generatingelectrode begins to produce massive product of oxygen. The oxygendischarges directly from the oxygen outlet.

New concept of the invention, utilizing the electrochemistry technologyand the system for producing and storing the hydrogen formed by thecombination of the zinc electrode and the gas-generating electrode inthe electrolyte, shown that of the electrochemical system for producingand storing hydrogen with high efficiency, high reliability, low costbeing used repeatedly, which obviously is different from all kinds oftraditional sources of hydrogen.

The differences are shown as follows:

I. Having safe, convenient character, and good controllability, as wellas size free adjusting property.

The process of producing and storing hydrogen, belongs to the batteryreaction, can be done under the condition of the normal temperature andnormal pressure. The output of hydrogen can be controlled only bycontrolling the amount of the electric current with the rapid andconvenient process of the operations of starting and stopping. Thesystem of this invention can be designed in the way of modularization.Therefore, it is easy for the disassembly, assembly and combination. Thesource of hydrogen can be made into the miniature and small size on alarge scale with movable or fixable model.

2. With high density of the stored energy, good purity of the hydrogengas and a wide working range of the invention.

It shows that the density of the stored energy of zinc itself is high.The purity of hydrogen produced in the condition of the strong baseelectrolyte is high, and working condition can be low temperature, therange of its application is wide.

3. Having characters of low cost, rich in the source of the rawmaterial, without pollution and in favor of environmental protection.

Because of an electrochemical reaction of zinc and water and what isstored in the system is water and zinc, the cost of the system ofpresent invention is greatly lower than the cost of the alloy forstoring hydrogen. In addition, it is rich in the zinc resource. Due tousing the raw materials that do not contain hydrargyrum, the inventioncan be used with safe and reliability and not resulting in environmentalpollution.

4. Having convenient and chargeable and reusable feature.

Because this system uses the way of charging to store the hydrogenenergy, therefore, it is not necessary to have inconvenient sources ofhydrogen such as a hydrogen station or hydrogen bottle. In other words,the hydrogen can be stored only by having electricity and water. It canalso be used repeatedly for many times.

5. The hydrogen gas and the electric energy producing at the same time.

When the hydrogen is to be released, the electric energy can be producedwithout an external electricity supply.

Lying with the advantages mentioned above, this invention has a greatapplication value in the aspect of portable and movable source ofhydrogen. Especially, it is suitable to provide hydrogen for hydrogenfuel cells. While providing the hydrogen, it can also generateelectricity as secondary product, which generates the electricitytogether with a fuel cell.

This invention is also suitable for the following technical fields:providing a convenient movable source of hydrogen environment withequipments such as the laboratory equipment and welding equipment; thecircumstances of jointly using electricity and hydrogen or exclusivelyusing electricity or hydrogen using a heat source, field lighting, etc.This invention can be also used in the aspect of energy storage. Forexample, the superfluous electric power is stored in the lowestelectricity-used period and the electric power generated by solar energyis stored. The energy storage ways are the joint storage of hydrogen andelectric energy.

DESCRIPTION OF THE INVENTION IN DETAIL EXAMPLE 1

Taking 1.5 g electric carbon black together with 6.0 g zinc oxides, 1.5g zinc powder without hydrargyrum, 3.3 ml polyvinyl alcohol aqueoussolution (concentration 3%), 25 ml sodium carboxymethyl celluloseaqueous solution (concentration 2%), 4 ml polytetrafluoroethylene (PTFE)emulsion (10% mass concentration), uniformly stirring and heating itinto a lump, rolling the lump into a sheet, pressing the sheet onto the60-mesh brass screen, which is taken as the zinc electrode. PPAT-AS-SL8film from Shanghai Shilong Company is as the diaphragm, foamed nickelsheet is as the oxygen-generating electrode, and the foamed nickel sheetthat is coated with Pt/C (Platinum is attached on the electric carbonblack) catalyst is as the hydrogen-generating electrode, 5 Mol/L KOHaqueous solution is as the electrolyte. The electrolyte submerges themost parts of the electrode.

The effective area of this single battery electrode is five squarecentimeters.

Constant Current Charge: The zinc electrode is connected to the negativepole, and the foamed nickel sheet is connected to the positive pole. Theelectric current is 50 mA charging for 3 hours. After charging, itstands for 15 minutes. When charging, the gas is produced on thepositive pole. No gas is produced on two poles when standing.

Discharge and Hydrogen Production: the zinc electrode is as the negativepole and the foamed nickel sheet that is coated with Pt/C catalyst is asthe positive pole. When the battery discharges, discharging current andvoltage are measured by using a universal meter. After the circuit issupplied, the electric current begins with 0.5 A furiously bubbling up.The gas production rate is up to 3.3 ml per minute. When reducing theelectric current, the gas production rate is reduced. If the circuit isnot supplied during the processing, hydrogen production stops. Whenswitching on the circuit again, the hydrogen production starts again. Inthis way, the charge and discharge are repeated for three times, and theelectric current and voltage slightly changed only and the same inphenomenon.

EXAMPLE 2

Taking 2.5 g zinc powder without hydrargyrum together with 7.5 g zincoxides, 3 ml polyvinyl alcohol aqueous solution (concentration 3%),mixing them into a slurry, applying it on the foamed nickel, after it isbaked to drying, it is pressed into a sheet, which is taken as the zincelectrode. The PPAT-AS-SL8 film is as the diaphragm, foamed nickel sheetis as the hydrogen-generating that is concurrently as theoxygen-generating electrode, 5 Mol/L NaOH aqueous solution is as theelectrolyte. The electrolyte submerges the most parts of the electrode.The effective area of the single battery electrode is ten squarecentimeters.

Constant Current Charge: The zinc electrode is connected to the negativepole, and the foamed nickel sheet is connected to the positive pole. Theelectric current is 60 mA charging for 5 hours. After charging, itstands for 15 minutes. When charging, the gas is produced on thepositive pole. No gas is produced on two poles when standing.

Discharge and Hydrogen Production: the zinc electrode is as the negativepole and the foamed nickel sheet is as the positive pole. When thebattery discharges, discharging current and voltage are measured byusing a universal meter. Switch on the circuit, the discharging currentis 70 mA and the voltage is 46 mV, bubbling up soon. After two hours,the voltage still is 65 mV while the discharging current is 36 mA.

Collecting the produced gas, the discharging begins with being up to 0.5ml per minute. When adjusting the electric current, in this way, chargeand discharge are repeated for three times, and the electric current andvoltage slightly changed only and the same in phenomenon.

EXAMPLE 3

Taking 0.5 g electric carbon black together with 7 g zinc oxides, 1.5 gzinc powder without hydrargyrum, polyvinyl alcohol 3.3 ml aqueoussolution (concentration 3%), 25 ml sodium carboxymethyl celluloseaqueous solution concentration 3%), 4 ml polytetrafluoroethylene (PTFE)emulsion (10% mass concentration), uniformly stirring and heating itinto a lump, rolling the lump into a sheet, pressing the sheet onto the60-mesh brass screen, which is taken as the zinc electrode. ThePPAT-AS-SL8 film is as the diaphragm, foamed nickel sheet is thehydrogen-generating that is concurrently as the oxygen-generatingelectrode, 5 Mol/L KOH aqueous solution is the electrolyte. Theelectrolyte submerges the most parts of the electrode.

The effective area of this single battery electrode is 12 squarecentimeters.

Constant Current Charge: The zinc electrode is connected to the negativepole, and the foamed nickel sheet is connected to the positive pole. Theelectric current is 100 mA charging for 5 hours. After charging, itstands for 15 minutes. When charging, the gas is produced on thepositive pole. No gas is produced on two poles when standing.

Discharge and Hydrogen Production: the zinc electrode is as the negativepole and the foamed nickel sheet is as the positive pole. When thebattery discharges, discharging current and voltage are measured byusing a universal meter. The electric current begins with 0.5 A, afteran hour, the electric current is 0.1 A, and after 3.5 hours, 62 mA,furiously bubbling up occurs as the charge begins. The gas productionrate is up to 3.3 ml per minute. When reducing the electric current, thegas production rate is reduced. When switching off the circuit, hydrogenproduction stops. When switching on the circuit again, the hydrogenproduction starts again.

In this example, the charge and discharge are repeated for three timesin the way of referenced above, there is slightly change in the electriccurrent and voltage and no change in phenomenon.

With regard to all the combinations and methods disclosed and revealedin this invention, the disclosed content in this document can be usedfor reference. Although they have been described partly by giving theexecutive examples, the people in this filed can change, splice, add orreduce this invention in the condition of not obviously divorcing fromthe contents, spirits and range, which are obvious to thoseprofessionals in this field. But their changes are included in thecontents, spirits and range in this invention.

1. An electrochemical method for producing and storing hydrogen in aclosed system consisting of a gas-generating electrode, an electrolyteand a zinc electrode, the gas-generating electrode and zinc electrodeare connected respectively to the external circuit; wherein switching onthe external circuit of the gas-generating electrode and zinc electrodethe hydrogen is to be released, the reduction reaction of water occurson the gas-generating electrode producing hydrogen, zinc is oxidized onthe zinc electrode generating the oxidation products of zinc; when thehydrogen is to be stored, supplementary water is supplied to the closedsystem, the negative pole of power source is connected to the externalcircuit of the zinc electrode, and the positive pole of power source isconnected to the external circuit of the gas-generating electrode,switching on the direct current, the oxidation products of zinc arereduced into zinc on the zinc electrode, renew the zinc electrode, theoxidation reaction of water occurs on the gas-generating electrode, theoxygen is generated and discharged.
 2. The electrochemical method forproducing and storing hydrogen described according to claim 1, whereinthe gas-generating electrode consists of the hydrogen-generatingelectrode and oxygen-generating electrode; or consists of thehydrogen-generating electrode that is concurrently as theoxygen-generating electrode.
 3. The electrochemical method for producingand storing hydrogen described according to claim 1, wherein the zincelectrode is made of zinc active substance, adhesive, additives,current-collecting device by using physical methods such as compacting,applying paste, agglomerating, boxing or piping, foaming,electrodeposition technology, and is composed of zinc active substanceselected from the group consisting of zinc alloy powder, zinc oxide,zinc hydroxide, zinc compound such as zincate or mixtures their of; theadhesive selected from the group consisting of carboxymethyl cellulose,polytetrafluoroethylene emulsion, polyvinyl alcohol, hydroxypropylemthylcellulose, polyethylene oxide, polyacrylic acid or polyvinylidenefluoride, hexafluoropropylene, or mixture thereof; the additivesselected from the group consisting of zinc oxides, calcium oxide,magnesium oxide, cadmium oxide, alumina, indium compounds, bismuthcompounds, lead compounds, calcium hydroxide, graphite powder, acetyleneblack, carbon powder, electric carbon black, active carbon powder,short-cut fiber, or carbon fibers, or mixtures thereof;current-collecting device being made of any one selected from the groupconsisting of foamed metal, metal mesh, metal tape (metal can be puremetal or alloy) by using the physical and chemical methods such aselectroplating, composite plating to treat the surface of the metal; andpreferably the punched brass strip, brass screen of the foamed brass,lead plating or tin plating.
 4. The electrochemical method for producingand storing hydrogen described according to claim 1, wherein the zincelectrode is a flaky or porous powder structure, and preferably theporous powder structure.
 5. The electrochemical method for producing andstoring hydrogen described according to claim 1, wherein the electrolyteis an aqueous solution electrolyte, and is absorbed by the batterydiaphragm, the pH of the aqueous solution is more than 4, andconcentration of the aqueous solution is in range of 0.05 Mol/L-15Mol/L; the hydroxide aqueous solution selected from the alkali metal oralkaline earth metal or their mixtures, the optimized selection is KOH,NaOH aqueous solution or their mixture, or selected from the groupconsisting of carbonate, sulfate, fluoride salt aqueous solution of thealkali metal or alkaline earth metal or mixtures thereof, or the mixturemixed with their hydroxide aqueous solution; the diaphragm is selectedfrom the group of materials consisting of hydrated cellulose film,polyethylene graft film, cellophane paper, nylon cloth, hydratedcellulose paper, cotton paper, potassium titanate paper, polyethylenefelt, zirconia fiber paper, vinylon non-woven fabric or mixtures of acomposite membrane thereof.
 6. The electrochemical method for producingand storing hydrogen described according to claim 1, wherein thehydrogen-generating electrode is made of pure metal, metal oxide, andthe composite materials made by the alloy or metal and alloy and oxide,by using several physical and chemical methods such as electroplating,composite plating, thermal decomposition, ion plating, ion implantation,ion sputtering, chemical plating, foamed metal technology, or made bycombining two or three kinds of technologies; the hydrogen-generatingelectrode selected from the group preferably consisting of pure metalsuch as Co, Fe, Mo, W, Pt, Pd, Ru; oxide such as RuO₂, TiO₂, ZrO₂; alloysuch as Ni—Mo, Ni—B, Ni—P, Ni—NiS, Ni—Pt, Ni—Ru, Co—Mo, Ni-Wo, Ni—Sn,Mo—W, Co—W, Ni-storing-hydrogen alloy, and Ni—P—Co—No—W, Ni—Co—Mo,Ni—Co—Mo—W, Ni—P—Mo—Co, Ni—P—W, Ni—P—Co—Mo—W, Ni—B—Co, Ni—B—Mo,Ni—B—Co—Mo, Ni—B—Co—Mo—W, Ni—B—W, Ni—Co-storing-hydrogen alloy;composite material of the metal or alloy with oxide such as Ni—RuO,Ni—Mo—RuO, Ni—NiS, Ni—Mo—W—RuO₂.
 7. The electrochemical method forproducing and storing hydrogen described according to claim 1, whereinthe oxygen-generating electrode is made of steel, iron, or nickel byusing methods of nickel plating, or sulfur coated nickel plating onstructures such as mesh, strip, plate, sheet, foamed metal to treat thesurface, or the electrode is any one selected from the group consistingof titanium-base platinum group oxide electrode, iridium system coatingtitanium electrode, manganese dioxide coating titanium electrode,perovskite type oxide electrode.
 8. The electrochemical method forproducing and storing hydrogen described according to claim 1, whereinthe hydrogen-generating electrode that is concurrently as theoxygen-generating electrode described is made of steel, iron, nickel byusing methods of the nickel plating or sulfur coated nickel plating onstructures such as mesh, strip, plate, sheet and foamed metal to treatthe surface.
 9. The electrochemical method for producing and storinghydrogen described according to claim 1, wherein the hydrogen-generatingelectrode, oxygen-generating electrode, and hydrogen-producing electrodethat is concurrently as the oxygen-generating electrode described arestructured flaky, meshy, porous, gas diffusion electrode.
 10. Theelectrochemical method for producing and storing hydrogen describedaccording to claim 3, wherein the zinc electrode is a flaky or porouspowder structure, and preferably the porous powder structure.
 11. Theelectrochemical method for producing and storing hydrogen describedaccording to claim 2, wherein the hydrogen-generating electrode is madeof pure metal, metal oxide, and the composite materials made by thealloy or metal and alloy and oxide, by using several physical andchemical methods such as electroplating, composite plating, thermaldecomposition, ion plating, ion implantation, ion sputtering, chemicalplating, foamed metal technology, or made by combining two or threekinds of technologies; the hydrogen-generating electrode selected fromthe group preferably consisting of pure metal such as Co, Fe, Mo, W, Pt,Pd, Ru; oxide such as RuO₂, TiO₂, ZrO₂; alloy such as Ni—Mo, Ni—B, Ni—P,Ni—NiS, Ni—Pt, Ni—Ru, Co—Mo, Ni-Wo, Ni—Sn, Mo—W, Co—W,Ni-storing-hydrogen alloy, and Ni—P—Co—No—W, Ni—Co—Mo, Ni—Co—Mo—W,Ni—P—Mo—Co, Ni—P—W, Ni—P—Co—Mo—W, Ni—B—Co, Ni—B—Mo, Ni—B—Co—Mo,Ni—B—Co—Mo—W, Ni—B—W, Ni—Co-storing-hydrogen alloy; composite materialof the metal or alloy with oxide such as Ni—RuO, Ni—Mo—RuO, Ni—NiS,Ni—Mo—W—RuO₂.
 12. The electrochemical method for producing and storinghydrogen described according to claim 2, wherein the oxygen-generatingelectrode is made of steel, iron, or nickel by using methods of nickelplating, or sulfur coated nickel plating on structures such as mesh,strip, plate, sheet, foamed metal to treat the surface, or the electrodeis any one selected from the group consisting of titanium-base platinumgroup oxide electrode, iridium system coating titanium electrode,manganese dioxide coating titanium electrode, perovskite type oxideelectrode.
 13. The electrochemical method for producing and storinghydrogen described according to claim 2, wherein the hydrogen-generatingelectrode that is concurrently as the oxygen-generating electrodedescribed is made of steel, iron, nickel by using methods of the nickelplating or sulfur coated nickel plating on structures such as mesh,strip, plate, sheet and foamed metal to treat the surface.
 14. Theelectrochemical method for producing and storing hydrogen describedaccording to claim 2, wherein the hydrogen-generating electrode,oxygen-generating electrode, and hydrogen-producing electrode that isconcurrently as the oxygen-generating electrode described are structuredflaky, meshy, porous, gas diffusion electrode.